The present invention relates to the field of imaging in general and to ultrasound imaging in particular.
Ultrasonic imaging has been applied in many two dimensional systems using pulse echo B-mode tomography or B-scans. These systems display echoes returning to an ultrasonic transducer as brightness levels proportional to echo amplitude. The brightness levels may be used to create cross-sectional images of the object in the plane perpendicular to the transducer aperture.
Examination of objects in three dimensions has evolved using a number of modalities including x-ray, ultrasound, and nuclear magnetic resonance. In particular, improvements have been made in spatial resolution, dynamic range, display methods and data analysis. For example, ultrasound scanning of three-dimensional objects by sequential B-scans followed by off-line reconstruction and display of rendered images has progressed in recent years with the introduction of commercial three-dimensional systems. Off-line rendering, however, may take several minutes to produce a single three-dimensional scan.
In the area of high-speed three-dimensional ultrasound imaging, U.S. Pat. No. 4,596,145 to Smith and von Ramm discloses an acoustic imaging system capable of producing high-speed projection orthoscopic images, as well as a single high-speed C-scan image using a two-dimensional array transducer and receive mode parallel processing. The C-scan image may be defined as a planar section of the object parallel to the effective transducer aperture. In 1987, U.S. Pat. No. 4,694,434 to von Ramm and Smith disclosed a steered array acoustic imaging scanner capable of producing a high-speed pyramidal scan to obtain a volumetric (three-dimensional) image using a two-dimensional array transducer and receive mode parallel processing.
High frequency intraluminal ultrasound imaging probes have been developed, including circular arrays and mechanically steered transducers. The circular arrays and mechanically steered transducers produce B-mode circular side scan geometries in which the ultrasound beam is swept through a 360xc2x0 arc. The 360xc2x0 arc may create a high-speed circular image within a vessel or lumen with a maximum range of approximately one centimeter. For example, U.S. Pat. No. 3,938,502 to Bom and U.S. Pat. No. 4,917,097 to Proudian, et al. disclose circular arrays of transducer elements within a catheter to produce a circular side scanning intraluminal B-mode image. U.S. Pat. No. 4,794,931 to Yock and U.S. Pat. No. 5,243,988 to Sieben, et al. disclose motor-driven piston transducers at the end of the catheters to produce circular side scanning intervascular imaging.
Catheters may be used in conjunction with the systems described above to provide intraluminal imaging. Intraluminal imaging may involve inserting a catheter, that includes an ultrasonic transducer phased array, into coronary vessels, pulmonary arteries, the aorta, or venous structures. For example, U.S. Pat. No. 5,704,361 to Seward, et al. discloses a volumetric imaging ultrasound transducer under-fluid catheter system. The advantages of Seward may, however, be limited by the quality of the imaging provided therein. In particular, the catheter probes disclosed in Seward show the therapeutic tools adjacent to the transducer array on the catheter tip, thereby reducing the area available for the transducer array. Such an array may provide images having reduced spatial resolution. Moreover, the applications described in Seward may be limited to procedures involving catheters.
The catheters described above may be combined with electrodes or tools to locate (cardiac electrophysiological mapping) and perform therapy on (radiofrequency ablation) or monitor tissue. For example, a three-dimensional ultrasound imaging device using a catheter may be combined with an ablation electrode to provide therapy to particular tissue. The therapy provided by the electrode, however, may be limited by the registration between the image provided by the catheter and the electrodes associated with the catheter. For example, a user may have difficulty translating the image produced by the catheter to the position of the electrode, thereby possibly creating difficulty in applying the electrode to the intended tissue. Moreover, the electrode may obscure the three dimensional ultrasound image when the electrode is within the field of view of the image.
In view of the above discussion, there exists a need to improve the quality of real-time three-dimensional imaging in intraluminal ultrasound applications.
In view of the above discussion, it is an object of the present invention to provide improved ultrasonic imaging probes.
It is another object of the present invention to provide improved therapy in conjunction with ultrasonic imaging.
These and other objects are provided by a real time three dimensional ultrasound imaging probe configured to be placed inside a body. The imaging probe includes an elongated body having proximal and distal ends. An ultrasonic transducer phased array is connected to and positioned on the distal end of the elongated body. The ultrasonic transducer phased array is configured to emit ultrasonic energy for volumetric scanning from the distal end of the elongated body and receive reflected ultrasonic energy. The ultrasonic transducer phased array includes a plurality of sites occupied by ultrasonic transducer elements. At least one ultrasonic transducer element is absent from at least one of the sites, thereby defining an interstitial site. A tool is positioned at the interstitial site. In particular, the tool can be a fiber optic lead, a suction tool, a scalpel, a guide wire, an electrophysiological electrode, or an ablation electrode. Positioning the tool at an interstitial site allows a large ultrasonic transducer phased array aperture, thereby producing superior image resolution and sensitivity as compared to the prior art. Conventional probes may include tools, positioned outside the ultrasonic transducer phased array, that reduce the aperture size of the ultrasonic transducer phased array. A reduced aperture size provides lower image resolution and sensitivity. Positioning the tool within the ultrasonic transducer phased array allows the user to accurately align the tool with the tissue to be treated more accurately, thereby making the probe easier to use and more effective.
In one aspect, a plurality of ultrasonic transducer elements are absent from a plurality of sites, defining a plurality of interstitial sites. The plurality of interstitial sites have a circular arrangement within the ultrasonic transducer phased array. The circular arrangement allows a larger aperture size while limiting side lobe effects on the imaging.
In another aspect, the ultrasonic transducer elements are arranged in a row of ultrasonic transducer elements and a column of ultrasonic transducer elements, defining four quadrants of interstitial sites within the ultrasonic transducer phased array. The row of ultrasonic transducer elements is substantially perpendicular to the column of ultrasonic transducer elements. A tool can be positioned at an interstitial site within each quadrant of the ultrasonic transducer phased array.
In still another aspect, a real time three dimensional ultrasound imaging probe apparatus is configured to be placed inside a body. The apparatus includes an elongated body having proximal and distal ends with an ultrasonic transducer phased array connected to and positioned on the distal end of the elongated body. The ultrasonic transducer phased array is configured to emit either forward or side scanning ultrasonic energy for volumetric scanning from the distal end of the elongated body and receive reflected ultrasonic energy. An electrode assembly is connected to and overlies the ultrasonic transducer phased array, wherein the electrode assembly is transparent to ultrasonic energy.
The ultrasonically transparent electrode assembly allows the user to more accurately apply the electrode to tissue within a region of interest, thereby allowing a reduction in the complexity associated with the prior art. For example, the present invention allows the user to apply the electrode to the tissue by locating the tissue within the region of interest using the real time three dimensional images. In contrast, users of some conventional imaging probes locate the tissue and then manipulate an electrode to the tissue by understanding the registration between the image and the physical location of the electrode on the probe.
The present invention also provides increased image resolution and sensitivity (signal to noise ratio) by increasing the aperture size of the ultrasonic transducer phased array to include a majority of the surface area of the distal end of elongated body. In particular, conventional ultrasonic transducer phased arrays cover a minority of the distal end of the elongated body described therein. Moreover, the prior art generally discloses an ultrasonic transducer phased array in conjunction with conventional tools and electrodes positioned in close proximity to the ultrasonic transducer phased array, thereby limiting the size of the ultrasonic transducer phased array. As a result, images produced by conventional imaging probes have less spatial resolution and sensitivity relative to those produced by the present invention.
The present invention also provides improved imaging over the prior art as applied to biopsy procedures. In particular, a real time three dimensional imaging biopsy apparatus configured to be inserted into a body includes an elongated body, having proximal and distal ends, that is configured to be extended through a biopsy needle into the body. An ultrasonic transducer phased array is connected to and positioned on the distal end of the elongated body. The ultrasonic transducer phased array is configured to emit and receive ultrasonic energy for volumetric scanning from the distal end of the elongated body.
The present invention also provides improved imaging over the prior art as applied to minimally invasive surgical procedures. In particular, a real time three dimensional ultrasonic imaging probe apparatus configured to be placed into a body, includes a cannula configured to provide access to a cavity inside the body. An elongated body, having proximal and distal ends, is configured to extend into the body via the cannula. An ultrasonic transducer phased array is connected to and is positioned on the distal end of the elongated body. The ultrasonic transducer phased array is configured to emit ultrasonic energy for volumetric scanning from the distal end of the elongated body and receive reflected ultrasonic energy.